Vapor plating with manganese, chromium, molybdenum or tungsten employing cyclopentadienyl metal carbonyl



United States Patent O Virginia No Drawing. Filed Aug. 11, 1960, Ser.No. 48,840

2 Claims. '(Cl. 117-1072) This invention relates to a process forproducing metallic coatings of metals of Groups VI-B, VII-B and VIII ofthe Periodic Chart of the Elements, Fischer Scientific Company, onappropriate substrates by decomposition of organometallic compounds ofsuch metals.

Present techniques for plating with the elements of Groups -VI-B, VII-Band VIII of the periodic chart of the elements are primarily limited toelectrolytic techniques. In some cases no techniques are known fordeposition of the metallic element. Moreover, these prior art techniquesare limited to the preparation of the ductile metal deposit and cannotbe adapted to the preparation of hard, excellently adherent commerciallyacceptable coatings of these metals. Furthermore, even deposition ofGroups VI-B, VII-B and VIII elements has been limited to the Well-knownhalides and pure carbonyls-that is those carbonyls wherein the carbonylgroup is the only substituent on the VIBVIII elementand consequently thereaction conditions at which the deposition process could be carried outhas also been severely limited. This lack of versatility in the priorart processes has resulted in uneconomical plating operations,oftentimes giving extremely unsatisfactory results. A process whichwould provide flexibility, particularly insofar as reaction conditionsand availability of compounds are concerned-a process which, because ofthe wide range of reaction conditions available, would produce metalliccoatings ranging from bright, essentially pure, excellently adheringcoatings all the way to extremely hard carbide coatings of therespective metalswould provide a considerable impetus to this area oftechnology. It would constitute a commercially feasible process for thedeposition of these elements.

It is therefore an object of this invention-to provide a flexible,economical process for the preparation of metallic coatings of GroupsVI-B, VII-B and VIII metals. It is a further object of this invention toprovide a process which produces extremely hard, well-adhering,excellent metal carbide coatings of the aforementioned metals as well asexcellent and essentially pure metal plates thereof.

These and other objects are accomplished in accordance with thisinvention by providing a process for plating a substrate which comprisesdecomposing a cyclopentadienyl transition metal coordination compound incontact with said substrate, the metal of the compound having an atomicnumber ranging from 8 through 12 less than that of the next higher raregas, the compound having a cyclopentadienyl group coordinated with themetal, the compound being stabilized by additional coordination with atleast one dilferent electron donating group capable of donating from 1through 4 electrons, and the sum of all coordinated electrons and theatomic number of the metal being equal to the atomic number of saidraregas.

By decomposition as used herein is meant any method feasible fordecomposing said cyclopentadienyl transition metal coordinationcompound. Thus the term includes roe decomposition by ultrasonicfrequency and decomposition by ultraviolet irradiation as well asthermal decomposition. Thermal decomposition, however, is the preferredmode of carrying out this invention because of its economicalsimplicity. I

Therefore, within the scope of this invention. is a process for platinga substrate which comprises heating the substrate to be plated to atemperature above the decomposition temperature of a cyclopentadienyltransition metal coordination compound, of a metal of atomic numberranging from 8 through 12 less than that of the next higher rare gas, incontact with said substrate; said compound having said cyclopentadienylgroup coordinated with said metal, the compound being stabilized by additional coordination with at least one electron donating group capable ofdonating from 1 through 4 electrons, the sum of all coordinatedelectrons and the atomic number of said metal being equal to the atomicnumber of said next higher rare gas.

In carrying out this latter embodiment it is preferred that thecyclopentadienyl transition metal coordination compound be acyclopentadienyl Group VI-B carbonyl, a cyclopentadienyl manganesecarbonyl or a cyclopentadienyl nickel nitrosyl. This preference is dueto the ready availability of these compounds, as well as to goodvolatility characteristics and stability exhibited thereby whichprovides for ease of handlinga factor extremely important in commercialproduction.

The metallic coatings produced by the process of this invention includeessentially pure metal plates as Well as extremely hard metal-containingcoats of metal carbides. The process of this invention has theparticular advantage in that through proper selection of processingconditions, the type of metal coating can conveniently and easily betailor-madevarying from essentially pure, bright metal plates all theway to hard metal carbide coats. For example, when a thermaldecomposition technique is employed in the process of this invention,essentially pure metal plates are produced at those temperaturesapproaching thedecomposition temperature of the cyclopentadienyltransition metal coordination compounds of this invention, and the metalcarbide coatings are increasingly produced as the temperature is raisedto a maximum, generally no higher than 600 C.

Thus one of the most significant advantages of the process of thisinvention is that it provides a process for producing metal coatings ofWidely diverse properties, which divergent coatings can simply andeconomically be produced in the same processing equipment without theneed of expensive engineering alterations. The commercial significanceof this advantage is quite apparent when consideration is given to thefact that a manufacturer need only invest in the very minimum ofprocessing equipment and yet is still able to produce a whole spectrumof metal coatings on a wide variety of substrates.

Metals of the Periodic System having an atomic number ranging from 8through 12 less than the next higher rare gas are metals of Groups VI-B,VII-B and VIII. Examples of the foregoing coordination compounds whichare employed in this invention are: cyclopentadienyl chromiumtricarbonyl hydride, cyclopentadienyl manganese tricarbonyl,bis(cyclopentadienyl iron dicarbonyl), cyclo pentadienyl cobaltdicarbonyl, butylcyclopentadienyl nickel nitrosyl,methylcyclopentadienyl molybdenum tricarbonyl hydride and the like.Methylcyclopentadienyl manganese tricarbonyl and cyclopentadienyl nickelnitrosyl are outstanding plating agents for use pursuant to thisinvention, especially from the cost-effectiveness standpoint.

In general, any prior art technique for metal plating an object bythermal decomposition of a metal-containing compound can be employed inthe present plating process as long as a cyclopentadienyl transitionmetal coordination compound as described above is employed as theplating agent (i.e., the metallic source for the metal plate). Forexample, any technique heretofore known for the thermal decompositionand subsequent plating of metals from the corresponding metal carbonylcan be employed. Illustrative are those techniques described by Landerand Germer, American Institute of Mining and Metallurgical Engineers,Technical Publication No. 2259 (1947). Usually the technique to beemployed comprises heating the object to be plated to a temperatureabove the decomposition temperature of the metal-containing compound andthereafter contacting the metal-containing compound with the heatedobject. The following examples are more fully illustrative of theprocess of this invention.

In Examples I-V the following technique is used:

Into a conventional heating chamber, housed in a resistance furnace andprovided with means for gas inlet and outlet, is placed the object to beplated. The or-' ganometallic plating agent is placed in a standardvaporization chamber provided with heating means, said vaporizationchamber being connected through an outlet port to the aforesaidcombustion chamber inlet means.

For the plating operation, the object to be plated is heated to atemperature above the decomposition temperature of the plating agent,the system is evacuated and the plating agent is heated to anappropriate temperature where it possesses vapor pressure of up to aboutmillimeters. In most instances, the process is conducted at no lowerthan 0.01 mm. pressure. The vapors of the plating agent are pulledthrough the system as the vacuum pump operates, and they impinge on theheated object, decomposing and forming the metallic coating. In mostinstances, no carrier gas is employed; however, in certain cases, acarrier gas can be employed to increase the efficiency of the abovedisclosed plating system. In those cases where a carrier gas isemployed, a system such as described by Lander and Germer, ibid., page7, is utilized.

Example I Compound 1 CpCr(CO) H. Compound temp. 100 C. Substrate Pyrex.Substrate temp 350 C. Pressure 0.1 mm. Time 3 hours. Result Brightmetallic coating.

1 Cyclopentadienyl chromium tricarbonyl hydride.

Example II Compound 1 CpMn(CO) Compound temp 90 C. Substrate Ceramic.Substrate temp 400 C. Pressure 2 mm. Time lhour. Result Metalliccoating.

1 Cyclopentadienylmanganese tricarbonyl.

Example III Compound 1 [CpFe(CO) Compound temp 100 C. Substrate Pyrex.

Substrate temp 350 C.

Pressure 0.5 mm.

Time 2 hours.

Result Metallic coating.

1 Bis-cyclopentadienyl iron dicarbonyl.

a method using higher temperatures.

Example 1V Compound 1 CpCo(CO) Compound temp. C. Substrate Pyrex.Substrate temp 500C. Pressure 0.1mm. Time lhour. Result Dark metalliccoating, very hard.

1 Cyclopentadienyl cobalt dicarbonyl.

Example V Compound 1 CpNi(NO). Compound temp. 50 C. Substrate A1 0pellets. Substrate temp 310 C. Pressure 2 mm. Time lhour. ResultMetallic coating.

1 Cyclopentadienyl nickel nitrosyl.

In the above examples the temperature utilized, i.e., in the vicinity of300 to 400 0, gives excellent metallic coatings. These metallic coatingsare generally very hard and exhibit excellent adherence to the substrateupon which deposited-the coats varying from bright metal plates all theway to extremely hard, dark metallic coatings, depending upon theprocessing conditions chosen.

The above processes employed resistance heating. The following workingexamples employ an induction heating In the latter process coatings ofsubstantial carbide content and exhibiting excellent characteristics areobtained.

The process employed in these examples is essentially the same as thatemployed in Examples I-V with the exception that the object to be platedis placed into a conventional heating chamber provided with means forhigh frequency induction heating, as opposed to the former process wherethe heating chamber was housed in a resistance furnace.

Example -V I Compound 1 MeCpMn(CO) Compound temp. 200 C.

Substrate Nickel coated mild steel.

Substrate temp. 600 C.

Pressure 0.2 mm.

Time .5 hours.

Resultv Hard, well-adherent coat- 1 Methylcyclopentadienyl manganesetricarbonyl.

Example VII Compound 1 CpCr(CO) NO. Compound temp. 200 C.

Substrate Nickel coated mild steel. Substrate temp 600 C.

Pressure 0.5 mm.

Time 1.5 hours.

Result Extremely hard, well-adherent coating.

1 Cyclopentadienyl chromium dicarbonyl nitrosyl.

In this Example VIII Compound 1 [CpW(CO) Compound temp .'260 C.

Substrate Mild steel.

Substrate temp 400 C.

Pressure 0.1 mm.

Result Dark metallic coating, very hard.

1 [Bis(cycpentadieny1 tungsten tricarbonyn].

Another method for decomposing the plating agent of this invention is bydecomposition with ultraviolet irradiation. The following example isdemonstrative of this technique.

The method of Example I is employed, with the exception that in place ofthe resistance furnace there is utilized for heating a battery ofultraviolet and infrared lamps placed circumferentially around theoutside of the heating chamber. The substrate to be heated is brought toa temperature just below the .decomposition temperature of the platingagent with the infrared heating and thereafter decomposition is effectedwith ultraviolet rays.

Example IX Compound 1 [Ind.Fe(CO) Compound temp 260 C. Substrate Pyrex.Substrate temp. 450 C. Pressure 1mm;

Result Hard, dark metallic coating.

1 Di (indenyl iron dicarbonyl).

By the term cyclopentadienyl, which is a substituent'in theaforementioned coordination compounds, is included substitutedcyclopentadienyl groups. The cyclopentadienyl moiety therefore includesalkyl and aryl substituted cyclopentadienyl groups, as well as indenyland fluorenyl derivativesincluding substituted indenyl and fluorenylderivatives. The term cyclopentadienyl preferably includes hydrocarboncyclopentadienyl groups containing 5 through about 17 carbon atoms.

Alternatively the cyclopentadienyl substituent of the transition metalcoordination compounds of this invention can be defined as a hydrocarboncyclomatic group. The term cyclomatic hydrocarbon includes cyclomatichydrocarbon radicals having from about 5 through about 17, or more,carbon atoms and embodying a group of 5 carbons having the configurationfound in cyclopentadiene. The cyclomatic hydrocarbon Group VI-B, VII-Band VIII metal coordination compounds of this invention are furthercharacterized in that the cyclomatic hydrocarbon radical is bonded tothe transition metal by carbon to metal bonds, through the carbons ofthe cyclopentadienyl group contained therein. Thus the cyclopentadienyltransition metal coordination compound can be represented by theillustrative formula wherein R represents a cyclopentadienyl moietycontaining a. 5 carbon ring (similar to that contained incyclopentadiene itself) coordinated to the Group.VI-B, VII-B or VIItransition metal, M, through the carbon atoms of the cyclopentadienylring; Q represents an electron donor group, or a combination of separateelectron donor groups, which can be the same or different from eachother, involved in covalent or coordinate covalent bonding with themetal atom and which donor groups are each capable of donating from 1through 4 electrons to the metal atom through said bonding; a has avalue of v 6 containing moieties. The cyclopentadienyl radicals canalternatively be considered as a cyclomatic radical such as 4,5,6,7tetrahydroindenyl, 1,2,3,4,5,6,7,8 octahydrofluorenyl; 3-methyl-4,5,6,7-tetrahydroindenyl, and 2- ethyl-3-phenyl-3,4,5,6,7-tetrahydroindenyl.

The constituents represented by Q in the above formula are electrondonating groups capable of coordinating with the Groups VI-B, V'II-B andVIII metal atoms of the compounds which are employed as plating agentsin the process of this invention. These groups are capable of sharingfrom l.through 4 electrons with the metal atom so that the metalachieves a more stable structure by virtue of such added electrons.These electron donating groups in coordination with the metal are,generally, either organic radicals or molecular spe cies which containlabile electrons. These electrons assume a more stable configuration inthe molecule when associated with the metal. The electron donating grouprepresented by Q may also'be inorganic entities which are capable ofexisting as ions, such as hydrogen, the cyanide group, and the varioushalogens. The halogens are representative of electron donating groupsdonating one electron and carbonyl illustrative of an entity donatingtwo electrons. An entity donating three electrons is represented by thenitrosyl group andaliphatic diolefins are illustrative of entitiescapable of donating four electrons. In those compounds which arepreferred plating agents in the process of this invention, Q representscarbonyl and nitrosyl electron donating entities which are capable ofdonating 2 and 3 electrons respectively.

The Group VI-B, VII-B and VIII metals which form the metallicconstituent of a coordination compound of this invention include themetals chromium, molybdenum, tungsten, manganese, technetium, rhenium,iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium andplatinum. Chromium, manganese, molybdenum, tungsten and nickel arepreferred because of their greater availability and excellent chemicaland refractory properties. Of these chromium and nickel are especiallypreferred because of their availability and excellent chemical and wearresistance properties. Furthermore, these last mentioned elements haveextremelywide' adaptability to a multitude of uses.

The following compounds further illustrate the types of Groups VI-B,VII-'B and VIII transition metal coordination compounds which can beemployed as plating agents in this invention. These compounds arecyclopentadienyl chromium tricarbonyl hydride, cyclopentadienyl chromiumdicarbonyl methyl, cyclopentadienyl chromium dicarbonyl nitrosyl,cyclopentadienyl chromium dinitrosyl chloride, octylcyclopentadienylmolybdenum tricarbonyl hydride, cyclopentadienyl molybdenum tricarbonylmethyl, cyclopentadienyl molybdenum tricarbonyl chloride,methylcyclopentadienyl molybdenum tricarbonyl methyl, cyclopentadienylmolybdenum tricarbonyl isopropyl, cyclopentadienyl molybdenum dicarbonylnitrosyl, bis(cyclopentadienyl molybdenum tricarbonyl) bis-[(methylcyclopentadienyl) molybdenum tricarbonyl], cyclopentadienylmolybdenum tricarbonyl hydride, cyclopentadienyl tungsten tricarbonylhydride, cyclopentadienyltungsten tricarbonyl ethyl, cyclopentadienyltungsten dicarbonyl nitrosyl, cyclopentadienyl manganese tricarbonyl,methylcyclopentadienyl manganese tricarbonyl, indenyl manganesetricarbonyl, acetylcyclopentadienyl manganese tricarbonyl,methylcyclopentadienyl manganese benzene, dicyclopentadienyl rhe' niumhydride, cyclopentadienyl rhenium tricarbonyl, cyclopentadienyl irondicarbonyl bromide, bis(cyclopentadienyl iron dicarbonyl),bis(methylcyclopentadienyl iron dicarbonyl), bis(ethylcyclopentadienyliron dicarbonyl), bis(indenyl iron dicarbonyl), bis(tetrahydroindenyliron dicarbonyl), cyclopentadienyl cobalt dicarbonyl, cyclopentadienylcobalt cyclopentadiene, cyclopentadienyl rhodium cyclopentadiene,cyclopentadienyl rhodium cyclo- 1,5-octadiene, cyclopentadienyl nickelnitrosyl, cyclopentadienyl nickel carbonyl iodide, bis(cyclopentadienylnickel carbonyl) and the corresponding Groups VI-B, VII-B and VIII metalcompounds containing ethyl cyclopentadienyl, butyl cyclopentadienyl,octyl cyclopentadienyl, dimethyl cyclopentadienyl, dihexylcyclopentadienyl, vinyl cyclopentadienyl, ethynyl cyclopentadienyl,phenyl cyclopentadienyl, methylphenyl cyclopentadienyl, acetylcyclopentadienyl, allyl cyclopentadienyl, benzyl cyclopentadienyl, tolylcyclopentadienyl, and other like radicals.

Any of the above compounds can be employed to plate their respectivemetallic constituent upon a multitude of substratesemploying any of thetechniques described hereinbefore-by controlling the'temperature of theplating operation, so that temperatures above the decompositiontemperature of the particular cyclopentadienyl coordination compound areemployed.

The term substrate as employed herein can be definedfurther as theobject to be plated and includes any material stable at the temperaturenecessary for the decomposition of the Groups VI- B, VII-B and VIIItransition metal coordination plating agents employed in this invention.Illustrative of various substrates are Pyrex glass and spun glass;various synthetic fibers and plastics such as polytetrafluoroethylene,polychlorotrifluoroethylene, rayon, nylon, Delrin (polyformaldehyderesin) and the like; steel, such as nickel plated steel, mild steel,nickel plated mild steel; metallic turnings such as copper, zinc and thelike; cellulose materials such as cotton, paper and the like-in short,any material stable under the plating conditions employed. Thus, furtherdemonstrative of the substrates of this invention are carbonaceousmaterials, such as graphite; other refractory substrates, such asCarborundum, ceramics, cermets and the like; other metallic substratessuch as aluminum, titanium, vanadium, yttrium, copper, zinc, cadmium andthe like; nuclear reactor fuel elements such as uranium 235, uranium233, thorium and other fissionable materials.

It should be noted that when employing the novel organo-metallic platingagents of this invention it is important to maintain enough vaporpressure below the decomposition temperature of the organometallicplating agent to enable the process to be conducted at an appreciablerate of plating. Too high vapor pressure results in somewhat inferiorsubstrate adherence. Thus, it is .preferred to employ up to about 10 mm.pressure during the plating operation-preferably 0.01 to 10 mm.pressure.

As has already been pointed out, temperatures are very important inobtaining the desired plated product. Thus, although temperatures abovethe decomposition temperature of the cyclopentadienyl transition metalcoordination compound of this invention can, in general, be employed inthe plating process, best results are attained within certain preferredtemperature ranges. For example, temperatures ranging from about 50 C.to about 250 C. above the decomposition temperature of the plating agentproduce very hard carbide containing products. Lowertemperaturesgenerally very near the decomposition temperature of theplating agent-are employed in the preparation of essentially pure metalplates.

The plating compounds of the present invention vary somewhat insofar astheir thermal stability is concerned but generally all of them can bedecomposed at a temperature above 400 C. Although temperatures as highas 700-750 C. can be employed the maximum temperatures utilized hereinare generally no higher than about 600 C.

In one embodiment of the instant invention mixtures of plating agents,each containing a different metal, are employed in the plating processto produce alloys of the respective metals upon appropriate substrates.An example is the utilization of cyclopentadienyl manganese tricarbonyland dicyclopentadienyl iron as plating-agents in a process similar tothat used in Examples I-V to produce an iron-manganese alloy depositupon various substrates.

The metal plates produced by the process of this invention find amultitude of uses in the aircraft, missile and chemical processingindustries. Thus aircraft and missile components which require ultrahigh quality performance characteristics such as resistance to hightemperatures, wear resistance and resistance to chemical attack cansatisfactorily meet these requirements when coated with a Group VI B,VII-B and VIII metal produced according to the process of the instantinvention.

The metal carbide coatings which are so conveniently prepared by theprocess of this invention find particular applicability in utilitieswhere their excellent high temperature and wear resistance propertiescome into play. Such applications are as coatings for dies, such as whenautomotive die is coated with nickel to produce a hard nickel metalliccoating by the process of the instant invention.

Having thus described and demonstrated the instant invention it is notintended that the scope thereof be limited in any way except as setforth in the following claims.

We claim:

1. A process for plating a substrate which process comprises:

(1) heating said substrate in an enclosed system to a temperaturemaintained within the range of from about 400 C. to about 750 C.,

(2) heating a cyclopentadienyl carbonyl compound of a metal selectedfrom the class consisting of manganese, chromium, molybdenum andtungsten, which compound is capable of being decomposed within saidtemperature range and contains in the molecule only one cyclopentadienylhydrocarbon group per metal atom, said heating being to a temperatureless than its decomposition temperature but sufiicient to generatevapors thereof,

(3) contacting said heated substrate with said vapors in said enclosedsystem while maintaining a pressure therein of from about 0.01 mm. toabout 10 mm. mercury, and

(4) continually contacting said heated substrate with said vapors untilthe desired thickness of coating is realized.

2. A process for effecting a manganese coating upon a substrate whichprocess comprises:

(1) heating said substrate in an enclosed system to a temperaturemaintained within the range of from about 400 C. to about 750 C.,

(2) heating a cyclopentadienyl manganese tricarbonyl compound capable ofbeing decomposed within said temperature range and containing in themolecule only one cyclopentadienyl hydrocarbon group per metal atom, toa temperature less than its decomposition temperature, but sufficient togenerate vapors thereof,

(3) contacting said heated substratewith said vapors in said enclosedsystem while maintaining a pressure therein of from about 0.01 mm. toabout 10 mm. mercury, and

(4) continually contacting said heated substrate with said vapors untilthe desired thickness of manganese coating is realized.

References Cited by the Examiner UNITED STATES PATENTS 2,818,416 12/1957Brown et al. 260-429 2,868,697 1/1959 Bingeman et al. 26042 9 2,930,7673/1960 Novak 117-107 2,955,958 10/1960 Brown 1l7-113 3,031,338 4/1962Bourdeau 117107.2 X

(Other references on following page) 9 UNITED STATES PATENTS 3,032,5725/1962 Fischer et 211. 3,061,464 10/1962 Norman et al. 1l7l07.2

FOREIGN PATENTS 7/1959 Germany.

OTHER REFERENCES Lander et al.: Plating Molybdenum, Tungsten and 10Chromium by Thermal Decomposition of Their Carbonyls, A.I.M.M.E.Technical Publication No. 2259, September 1947; pp. 6 and 7 relied on.

Powell et al.: Vapor Plating (1955), John Wiley and Sons Inc. (N.Y.);pp. 1-4 relied on.

RICHARD D. N-EVIUS, Primary Examiner.

R. E. HOWARD, A. GOLIAN, Assistant Examiners.

1. A PROCESS FOR PLATING A SUBSTRATE WHICH PROCESS COMPRISES: (1)HEATING SAID SUBSTRATE IN AN ENCLOSED SYSTEM TO A TEMPERATURE MAINTAINEDWITHIN THE RANGE OF FROM ABOUT 400*C. TO ABOUT 750*C., (2) HEATING ACYCLOPENTADIENYL CARBONYL COMPOUND OF METAL SELECTED FROM THE CLASSCONSISTING OF MANGANESE, CHROMIUM, MOLYDENUM AND TUNGSTEN, WHICHCOMPOUND IS CAPABLE OF BEING DECOMPOSED WITHIN SAID TEMPERATURE RANGEAND CONTAINS IN THE MOLECULE ONLY ONE CYCLOPENTDIENYL HYDROCARBON GROUPPER METAL ATOM, SAID HEATING BEING TO A TEMPERATURE LESS THAN ITSDECOMPOSITION TEMPERATURE BUT SUFFICIENT TO GENERATE VAPORS THEREOF, (3)CONTACTING SAID HEATED SUBSTRATE WITH SAID VAPORS IN SAID ENCLOSEDSYSTEM WHILE MAINTAINING A PRESSURE THEREIN OF FROM ABOUT 0.01 MM. TOABOUT 10 MM. MERCURY, AND (4) CONTINUALLY CONTACTING SAID HEATEDSUBSTRATE WITH SAID VAPORS UNTIL THE DESIRED THICKNESS OF COATING ISREALIZED.